Forgot about this topic. We had a bit of an engineering lecture in the SB the other day, run by yours truly
I was basically explaining what is wrong with saw, and it comes down to a very basic design flaw.
The front row overhangs the front wheel bogies by quite some distance, which over the years has placed undue stress on the pilot pivot/coupler between the two rows (see diagram below).
The "roughness" is actually mostly on the front row, with the back row not affected as much, as it's supported by wheel bogies both in front, and behind the row.
Because of the extra "play" in the pilot car joint, the front row actually bounces in front of the front wheel bogies, when under high G-forces. Next time you are on it you will notice it now I've said it.
Here's a basic diagram explaining what is causing the problem, followed by the best side-on view of one of the cars I could find:
(from Google image search)
As you can see by the diagram, there will be excessive "leverage" force being applied to the pivot point due to the sheer amount of force applied to the right of the fulcrum. This force is further multiplied by the massive difference in length between the pilot to the fulcrum, and fulcrum to the front of the car, and futher multiplied under the force of gravity.
This force will be further enhanced from the back rows weight, also pushing down on this joint, but not as severe due to the support from the rear wheel bogies.
To any mechanical engineer, this is a fundamental design flaw, that is obvious to anyone with even a basic engineering education, so how/why Gerst seemed to miss it, I will never know.
I can only hope the positioning of the wheels on The Smiler is further forward, or has been addressed in some other way, other wise it will fall prey to the same degradation of smoothness that Saw has experienced. It's difficult to tell from the current images, but it does look like the bogies DO attach further forward on Smiler's chassis, so all hope is not yet lost
Hope this has been enlightening for you all